docs: match task validation errors to current API responses
A developer following the task reference can misread rejected requests: POST advertises an integer error and message, and PATCH requires a field path that malformed JSON does not include. Correct both 400 responses to the released API's status, text error and optional missing_fields; add copyable malformed-JSON and numeric-schedule examples. Both operations reuse the existing concrete schema so its published name and the website's single-reference renderer remain compatible.
Freeze the two responses through the existing shared fixture producer and API regression tests, then regenerate the complete AI reference. Only the task-create and task-update document bodies change; all 240 documents and 237 JSON blocks remain. Request formats, successful responses and API behavior are unchanged. Related: recoupable/mono#318 and recoupable/mono#360. The separate proposed schedule-syntax validation in API #1100 is not described as released here.
API companion #1101 is merged as e47d32e6051150d6af45c6f5df25bade0cba8891, and this inventory pins that actual revision. The refresh changes only apiSourceCommit; all authored/generated documentation and shared fixture bytes are unchanged from the reviewed contribution. Retained Docs publication follows the actual Marketing merge through the normal provenance sync. No manual deployment or original customer-ticket closure is included.
Validation: 506 website tests, 28 fixture-producer tests, docs generation/reference checks, source-inventory and both-fixture checks, lint (0 errors; 39 existing warnings), and the normal local production build pass. The companion API's 225 contract tests and response-constructor type check pass; its full-project type check retains the same 211 inherited diagnostics. All task checks are synthetic and do not create, update or run a stored task.
Summary by cubic
Corrects the task POST/PATCH 400 error documentation to match the released API: both previously advertised an integer error and message, and PATCH required missing_fields even when the body is not valid JSON.
Both responses now document the API's status, text error, and optional missing_fields (omitted for malformed JSON), with copyable malformed-JSON and numeric-schedule examples. A new shared fixture producer freezes the two responses, and the inventory pin was refreshed to the merged companion API revision. Only the task-create and task-update document bodies change; request formats, successful responses, and API behavior are unchanged.